bad B fields in commit-aside

After further poking around we discovered another problem using commit-aside in Python. If you have a view that has a binary B property then some part of the full commit does not seem to work. If the view has no B properties then we can do a full commit and nuke the aside file with no consequences, but if there is a B property we can reliably crash the python process due to something in Mk4py.dll exploding. The following code snippet should recreate the problem.

  import metakit, random, os
  db = metakit.storage("_f.mk", 1)
  dba = metakit.storage("_f.mka", 1)
  db.aside(dba)
  vw = db.getas("a[i:I,b:B]")
  vw.append(i=1,b=random.getrandbits(32))
  vw.append(i=2, b=random.getrandbits(32))
  vw.append(i=3, b=random.getrandbits(32))
  dba.commit()
  db.commit(1)
  del vw
  del db
  del dba
  os.remove("_f.mka")
  db = metakit.storage("_f.mk", 1)
  dba = metakit.storage("_f.mka", 1)
  db.aside(dba)
  vw = db.getas("a")
  assert len(vw) == 3
  # and now to crash things
  assert vw[0].i == 1

If none of the view properties are binary then everything will work as expected (modulo the "open the views before trying a full commit" bit Zooko noted) but with a binary property in the mix then as soon as we try to use the re-opened views after doing a full commit and nuking the aside file everything comes crashing down.

Regards,

Jim McCoy

Summary

Commit aside has several known limitations and will probably never be fixed.